1. Field of the Invention
The present invention relates to a variable compression ratio apparatus, and more particularly, to a variable compression ratio apparatus for varying a compression ratio of mixed gas inside a combustion chamber according to an operation condition of an engine.
2. Description of Related Art
In general, thermal efficiency of a heat engine is increased when a compression ratio is high, and thermal efficiency of a spark ignition engine is increased when an ignition timing is advanced up to a predetermined level. However, when the ignition timing is advanced in a high compression ratio, abnormal combustion may be generated in the spark ignition engine, which causes damage to an engine, such that there is a limit in the advance of the ignition timing and thus it is necessary to bear output deterioration.
The variable compression ratio (VCR) apparatus is an apparatus for changing a compression ratio of mixed gas according to an operation condition of an engine. According to the variable compression ratio apparatus, fuel efficiency is improved by increasing the compression ratio of the mixed gas in a low load condition of an engine, and a generation of knocking is prevented and an engine output is improved by decreasing the compression ratio of the mixed gas in a high load condition of an engine.
In the variable compression ratio apparatus in the related art, a change in a compression ratio is implemented by changing a length of a connecting rod for connecting a piston and a crankshaft. Such a type of variable compression ratio apparatus, a part for connecting the piston and the crankshaft includes a plurality of links, so that combustion pressure is directly transferred to the links. Accordingly, durability of the links deteriorates.
Accordingly, a method of separately connecting the crankshaft to the piston without directly installing the variable compression ratio apparatus on the crankshaft has been researched. As a result of various experiments for the variable compression ratio apparatus, an apparatus of changing a compression ratio by using an eccentric bearing has attracted attention due to high operational stability. However, there is a problem in that it is difficult to combine the links for rotating the eccentric bearing without disturbing the rotation when considering a position and an operation condition of the crankshaft.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.